Document alignment system

ABSTRACT

A document alignment system comprises a feed system ( 6 ), defining an elongate path, for feeding documents along the path. The feed system is adjustable to vary the orientation of the elongate path in a lateral plain so as to cause a document to undergo a corresponding lateral shift as it is moved along the path. A detector ( 25,26 ) detects the lateral position of a document upstream of the elongate path. A control system ( 70,17,17 ′) is responsive to the detector ( 25,26 ) to adjust the feed system ( 6 ) so that the document undergoes a desired amount of lateral movement as it is moved along the elongate path.

The invention relates to a document alignment system, for example foraligning documents of value such as banknotes.

In conventional document processing systems, documents are transportedalong a path so that they can be inspected for authenticity, value orthe like and then directed to a suitable destination. Examples of suchequipment include banknote sorting equipment, letter sorting equipmentand the like. One of the problems with such equipment is that thedocuments must be transported in accurate alignment so that informationcan be detected from them. In many such types of equipment, thedocuments are supplied only roughly organised into alignment and thisreduces the efficiency of the apparatus. In this context, alignmentrefers to the lateral position of a document relative to the transportdirection and should be contrasted with skew which represents a degreeof twist imparted to the document.

U.S. Pat. No. 5,577,719 describes a document alignment system in which adocument is supplied to an alignment position in which a set oftransversely arranged rolls can be selectively energised to move thedocument while it is held in the alignment position. Thereafter, thedocument feed is reactivated and the aligned document fed onto the nextstage in the process. The problem with this approach is that thedocument feed has to be stopped while alignment is carried out.

EP-A-0577928 illustrates a document transport system including analignment roller mounted on a shaft which can be pivoted through a smallangle depending upon the degree of realignment required. This system canonly achieve minimal realignment.

U.S. Pat. No. 5,219,159 describes a sheet de-skew and registrationdevice in an electrophotographic printing machine. A sheet is de-skewedby driving its leading edge into a nip between two pairs of stalled orstationary rollers and then, whilst transporting the sheet between theserollers, the roller pairs and sheet are moved laterally to a requiredposition set by detection of the edge of the sheet. The problem withthis system is the need to stop the rollers to achieve part of therealignment process which restricts the speed at which the machine canoperate.

DE-A-2509276 describes an alignment mechanism for transportingoverlapped sheets. The sheets are transported on a series of parallelbelts which are angled to the nominal sheet feed direction in order tourge one edge of the sheets towards a transport side guide. The angle ofthese belts is adjusted manually prior to operation of the system. Inthis case, it is essential that all sheets fed to the alignmentmechanism have a known orientation which means that this system is notsuited to many situations in which the alignment of documents is notknown.

In accordance with one aspect of the present invention, a documentalignment system comprises a feed system, defining an elongate path, forfeeding documents along the path, the feed system being adjustable tovary the orientation of the elongate path in a lateral plane so as tocause a document to undergo a corresponding lateral shift as it is movedalong the path; a detector for detecting the lateral position of adocument upstream of the elongate path; and a control system responsiveto the detector to adjust the feed system so that the document undergoesa desired amount of lateral movement as it is moved along the elongatepath.

In accordance with a second aspect of the present invention, a method ofaligning documents comprises supplying documents to a document alignmentsystem according to the first aspect of the invention; detecting thelateral position of each document; and adjusting the feed system tocause the document to undergo a desired amount of lateral movement asthe document moves along the elongate path.

This invention overcomes a number of different problems with the priorart set out above. Firstly, rather than changing the lateral position ofa feed nip, the orientation of the elongate path itself is adjusted andthis allows much more accurate control of the feeding of sheets to beachieved which is particularly important in the case of old sheets suchas used currency and for achieving high speed operation as found inbanknote dispensing and sorting apparatus.

In addition, the system enables automatic alignment of documents to beachieved by detecting the lateral position of the document upstream ofthe elongate path and adjusting the feed system accordingly. Typically,that adjustment will be to centralize the document but in other casesthe document could be aligned with any datum position.

A further important advantage of this invention is that it enables adocument to be aligned relative to any datum i.e. a “virtual datum”system. This should be contrasted with known alignment systems in whichdocuments are aligned against a fixed datum wall.

This alignment is achieved by the control system adjusting the feedsystem to the appropriate lateral position. Conveniently, this isachieved by a control system including a detector which can detect thelateral position of the feed system. The control system detector couldsimply detect a part of the feed system but preferably the feed systemincludes an indicator which moves laterally with the feed system and isdetected by the detector of the control system.

The use of a special indicator enhances the accuracy of the operation ofthe control system and allows the indicator to have a special form forexample a form which varies in the lateral direction so its direction ofdisplacement can be uniquely determined. In the preferred example, thisindicator or flag has a wedge shape.

The control system could include a moveable detector which is moved inresponse to the desired amount of lateral movement of the document, thecontrol system always centering the indicator with the detector (orpositioning it within a predetermined distance of the detector). Moreconveniently, however, the control system detector is fixed and thecontrol system adjusts the position of the feed system until therelative locations of the indicator and control system detector are suchthat a document will undergo the desired amount of lateral movement.

In one implementation, the feed system can comprise a set of rollersspaced apart along the elongate path, a number, typically all, of therollers being laterally adjustable. However, in the preferredarrangement, the feed system comprises at least one endless belt. Thishas the advantage over the use of rollers in that it is simpler inconstruction and requires less motive power to adjust the feed system.

The control system may be arranged to adjust the position of the endlessbelt(s) at a location adjacent a downstream end of the elongate path, alocation adjacent an upstream end of the elongate path, or at bothlocations. In the latter event, it is then possible also to de-skew thedocument.

In some cases, the feed system will define just a lower surface of theelongate path but in the preferred arrangement, the feed systemcomprises a plurality of endless belts arranged in upper and lowerlaterally spaced sets relative to the elongate path, each belt of theupper set being laterally offset from adjacent belts of the lower set.This allows more complete control of the passage of documents to beachieved while laterally spacing the belts apart has been found toimprove overall operation of the system.

Typically, the feed system comprises a pulley mounted on a shaft, thepulley being coupled to the control system for lateral displacement. Thepulley could form part of the feed system defining the elongate path(i.e. a roller as discussed above) or an endless belt could be entrainedaround the pulley.

The pulley could be slidably mounted on a shaft for lateral movement butpreferably is mounted for lateral movement with the shaft. This enablesthe lateral movement to be achieved by moving the shaft from a positionremote from the pulley. Typically, the pulley will be nonrotatablymounted to the shaft so that it can be easily driven from the shaftalthough this is not essential. For example, the pulley could berotatably mounted to the shaft and then driven from a separate driveroller which engages the pulley.

In some cases a further detector could be provided downstream of thefeed system so as to check whether or not the documents are now aligned.

As mentioned previously, the document alignment system can be used in awide variety of applications including document processing equipmentsuch as banknote dispensers, acceptors, sorters and recyclers. In theseapplications, the alignment system will normally be provided upstream ofthe remainder of the document processing, however, it is envisaged thesystem will be of use at intermediate stations in longer documenttransporting systems.

Examples of banknote alignment systems according to the presentinvention will now be described with reference to the accompanyingdrawings, in which:

FIG. 1 is a schematic, perspective view of a first bank note alignmentsystem from above and one side;

FIG. 2 is a schematic, perspective view of FIG. 1 from above and theother side;

FIG. 3 is a view similar to FIG. 1 but with some parts omitted;

FIG. 4 is a view similar to FIG. 2 but with some parts omitted;

FIG. 5 is a plan of FIG. 1 with some parts, including the flag, omitted;

FIG. 6 is an end view of FIG. 1;

FIG. 7 is a schematic plan of the main components of the apparatus shownin FIG. 1;

FIG. 8 is a block diagram of the control system;

FIG. 9 is a schematic, perspective view of a second bank note alignmentsystem from above and one side; and,

FIG. 10 is a plan view of FIG. 9.

The banknote alignment system shown in the drawings is in the form of amodule 1 having a pair of side plates 7,8 held spaced apart by a set ofspacers 9. A set of pulleys 4 are mounted non-rotatably to a shaft 2journalled between the side plates 7,8. A second set of pulleys 5 offsetrelative to the pulleys 4 are non-rotatably mounted on a shaft 3journalled between the side plates 7,8 (FIG. 4). The sets of rollers 4,5define an inlet to the module 1 for documents. The ends of the shafts2,3 where they project through the plate 8 carry respective ones of apair of intermeshing gears 40,41 fixed, non-rotatably, to the shafts2,3. The gear 41 meshes with an earlier stage of the sheet transportmechanism located at 200. Thus, the motor used to drive the sheettransport mechanism 200 is also used to drive the shafts 2,3.

Towards the other end of the module 1 are positioned a second pair ofupper and lower shafts 11,13, each carrying a respective set of pulleys10,12 (FIG. 3). Pulleys 12 are offset from pulleys 10 in a mannermatching the arrangement between pulleys 5 and 4. The shafts 11,13 aremounted in bearings (not shown) in each of the side plates 7,8 andattached to each other by respective link plates 18,18′ at each end insuch a way that allows them to be moved at right angles to the sideplates so as to traverse the pulleys 10,12 maintained in their relativeoffset positions, to and fro between the side plates 7,8.

A set of suitably profiled belts (for example “O” ring or “T” section) 6are entrained around respective pairs of the pulleys 4,10 and 5,12. Thelower section of each upper belt 6 and the upper section of each lowerbelt 6 define a document transport path from the inlet to the module 1towards the outlet.

In practice, the diameters of the pulleys 4,5 (and similarly pulleys10,12) vary depending upon their lateral position. This is shown mostclearly in FIGS. 5 and 6 where it will be seen that the pulleys 4comprise a pair of inner, larger diameter pulleys 4A and laterallyouter, smaller diameter pulleys 4B. Similarly, the pulleys 5 comprise aset of three inner, larger diameter pulleys 5A and four outer, smallerdiameter pulleys 5B. As can be seen in FIG. 5, the pulleys 10 comprise apair of inner, larger diameter pulleys 10A and a set of outer, smallerdiameter pulleys 10B. The pulleys 12 comprise a set of three inner,larger diameter pulleys 12A and a set of outer, smaller diameter pulleys12B. The result of using these different diameter pulleys is that sheetsassume a corrugated cross-sectional shape as they are transported.Furthermore, pulleys 4B and 5B (and similarly 10B and 12B) are of adiameter which provides a clearance between the nominal flat sheettransporting position and the upper surface of the lower transportingbelt 6B between rollers 5B and 12B and the lower surface of the uppertransporting belt 6B between the rollers 4B and lOB. Belts 6B,therefore, provide moving guides to support the outer ends of sheetsbeing transported through the system.

A further pair of shafts 20,22 are journalled between the side plates7,8 and carry respective sets of pulleys 19,21 non-rotatably mounted tothem (FIGS. 1 and 3). These pulleys are aligned and the nips between thepulleys 19,21 are aligned across the nominal sheet transport pathdefined by the belts 6 at the outlet end of the feed path. The shafts20,22 protrude through the side plate 8 where intermeshing gears 45,46respectively are non-rotatably mounted to them.

The shaft 20 also protrudes out from the side plate 7 and carriesnon-rotatably a pulley 23 about which is entrained a toothed drive belt24 (FIG. 4). The belt 24 is also entrained about a pulley 23′non-rotatably mounted to the shaft 3 where it protrudes through the sideplate 7 so that the shaft 20 is driven from the shaft 3.

As a result, the pulleys 4 rotate anti-clockwise looking from the sideplate 8 towards the side plate 7 and the pulleys 5 rotate clockwise. Thepulleys 21 rotate anti-clockwise and the pulleys 19 clockwise.

As will be appreciated from the description above, the lateral positionof the pulleys 10,12 is adjustable by suitably moving the shafts 11,13.In this example, movement is obtained by suitably controlling a pair ofstepping motors 17,17′ attached to the side plates 7,8 respectively.Each stepping motor 17,17′ is connected to a respective drive pulley16,16′ around which is entrained a belt 15. The belt 15 is secured to abracket 14 (FIG. 3) which is also secured to the shaft 11. Thus, bysuitably operating the stepping motors 17,17′, the belt 15 is moved toand fro between the side plates 7,8 causing corresponding movement ofthe shafts 11,13.

A U-shaped optical sensor 51 is mounted to a support So between the twoside plates 7,8. The U-shaped sensor 51 is designed to determine whenthe displaceable carriage, formed by shafts 11,13, is in a centralposition, to the right of the central position or to the left of thecentral position with respect to the two side plates 7,8. This isachieved by having a flag 14 a mounted on the bracket 14 (FIG. 3), theflag 14 a having a lateral, wedge shaped extension 14 b. The U-shapedsensor 51 and the flag 14 a are positioned such that when thedisplaceable carriage is in the central position, the extension 14 b ofthe flag 14 a (FIG. 3) will be located between the arms of the U-shapedsensor 51 at the approximate central position. This will be used by themicroprocessor 70 (discussed below) to determine when the carriage is inthe central position. when the flag 14 a increasingly obscures theU-shaped sensor 51 the displaceable carriage will be positioned awayfrom the central position towards the side plate 7 and when the flag 14a obscures the U-shaped sensor 51 less the displaceable carriage will bepositioned away from the central position towards the side plate 8. Thisprovides feedback to the microprocessor 70 enabling it to confirmcorrect operation of the motors 17,17′.

The amount of displacement of the displaceable carriage is thenmonitored by a tachometer 52, which is provided on the motor 17. Thetachometer 52 consists of a timing disk 52A and a quadrature opticalsensor 52B (FIG. 5) which allows the position of the motor 17 to bemonitored. A signal representative of the motor position is fed to themicroprocessor 70 which then uses this information to track the motionof the displaceable carriage from when it was last in the centralposition. This allows the microprocessor 70 to determine the currentdisplacement of the carriage from the central position.

A number of sensors 25,26 are supported above and below the feed pathrespectively on a U-shaped bracket 28 attached to the side plate 7. Thesensors 25 and 26 are to monitor the progress of the notes through thecentraliser mechanism 1. Used in conjunction with a shaft encoder (notshown) and knowing the mechanical geometry they can be used to trackwhere the notes are within the transport at any time. This is veryimportant as the displaceable carriage, formed by shafts 11,13 shouldnot be displaced in a lateral direction whilst a note is in the gapbetween shafts 11,13 and 20,22 as the note is pinched by the pulleys oneach of these shafts and lateral movement during this transition wouldtear the note. The purpose of the sensors 25,26 is to allow themicroprocessor 70 (discussed below) to monitor the position of the notesas they pass through the centraliser and determine the time when thecarriage may be displaced. In the case of a single note passing throughthe system, this may not be crucial, but in the case where a stream ofnotes is to be centralised, this information is critical to thesuccessful operation of the unit. Two laterally spaced sensor pairs25,26 are used in this case to allow the skew of the note to be measuredand allowance made for its increased effective length as a result of anyskew.

As can be seen in FIG. 7, the module 1 is located between a sheettransport system 200 for transporting sheets 400 one by one to themodule 1 and a downstream sheet transport 300 for transporting the sheetexiting the module 1 towards its eventual destination. A detectorarrangement 60 which may be of any known type is provided fordetermining the position of moving sheets as they reach the module 1,the sheets being transported to the pulleys 4,5 by rotation of a shaft201 carrying pulleys 202. The detector arrangement 60 determines thelateral offset of an incoming sheet 400 which may, for example, beaccurately aligned as shown in solid lines in FIG. 2 or laterally offsetto a position 400A as shown in dashed lines. The detector arrangement 60is connected to a microprocessor 70 (FIG. 8) which generates an outputsignal on a line 71 which is fed to a motor control circuit 72 whichcontrols the stepper motors 17,17′.

The detector arrangement 60 could be implemented in a number ofdifferent ways. A typical method would be a linear array of lightemitting devices, and photoreceivers (photodiodes or photoresistors),placed either side of the note path, such that the note will break thebeams between the devices. If these devices are placed on say a 1 mmpitch then the lateral position of the note can be determined quiteaccurately by monitoring the number of devices that are blocked on eachside as the note passes.

An alternative approach is to use two rectangular large areaphotodiodes, each illuminated by a similarly shaped light source, thesebeing placed as shown in FIG. 7. In this instance, as the note passesbetween the emitter and sensor on each side, it will partially block thelight passing between them, the proportion of light being blocked givinga measurement of the amount of note between them. If the two sensors aresimilar and if the note is centrally placed then the proportion blockedon each side will be the same, if the note is offset then the proportionwill be different on each side, the amount of difference giving ameasurement of the offset of the note.

By allowing both ends of the belts to be laterally shifted, skew inducedin the sheets during alignment correction can also be corrected. In thismodification (which is described later), the detector 60 would also beused to determine the extent of skew and further drive means similar tothat shown to drive shafts 11,13 will be needed to drive the shafts 2,3.

In a further possibility, a sensor arrangement already present, forexample for use in pattern detection, could also be utilised todetermine the location of the edges of notes.

Documents fed through the module 1 are supplied to friction drive belts301 of the downstream transport 300.

In operation, a sheet 400 is normally transported towards its eventualdestination in a manner in which the leading edge of the sheet is,within acceptable limits, at right angles to the direction in which thesheet is being transported. In addition, the sheet is transported,within acceptable limits, along a predetermined path in which the sheetis positioned such that its transport direction centre line is on thecentre line of the transporting media arrangement. In this normalarrangement, the module 1 is operated with the pulleys 10,12 located sothat the belts 6 run normally parallel to the side plates 7,8 as shownat 6 a in FIG. 7.

In the event that a sheet 400 being transported is not correctlypositioned laterally as shown at 400A, then this will be sensed by thedetector arrangement 60. The microprocessor 70 computes from the amountof displacement how much the sheet must be displaced laterally tocompensate and bring it back to a centralised position.

Once this has been calculated, the microprocessor 70 uses the positioninformation determined from the sensor 51 and the tachometers 52,52′ todetermine the current position of the displaceable carriage. Themicroprocessor 70 then calculates the distance between the currentcarriage position and the carriage position required to centralise thenote and uses this information to control the motors 17,17′ therebyplacing the displaceable carriage in the correct position. The motorsare generally controlled to operate at one of three different speeds,with a slow speed being used for small displacements and a faster speedbeing used for larger displacements. The system preferably uses theslowest speed, wherever possible, as this results in more reliablepositioning.

Once the microprocessor 70 has determined the suitable position for thedisplaceable carriage the microprocessor 70 outputs a suitable signal onthe line 71 to the motor control circuit 72 which activates the motors17,17′ to drive the drive belt 15. In the example shown in FIG. 7, thedocument must be laterally offset towards the plate 7. Consequently, theshafts 11,13 are moved from the side plate 8 towards the side plate 7 sothat the belts 6 take up the positions 6 b shown in dashed lines in FIG.7. As the sheet 400A continues to be fed into the module 1, it will begripped between the belts 6 now located in the position 6 b and as it istransported through the module 1, it will also be shifted laterallytowards the side plate 7 so that the centre line of the sheet as itexits the module 1 is realigned with the centre line of the module.

As indicated in FIG. 8, an optional detector arrangement 60′ could bepositioned at the exit end of the module 1 to verify that the sheet hasnow been correctly positioned.

In alternative constructions, more than one alignment system could beused either one after the other or spaced serially at intervals along asheet transport path.

In a further alternative construction, the self-centralising propertiesof the belt system can be utilised to eliminate the need for a doubleacting drive arrangement. Such an arrangement has cost benefits wherethe speed at which the sheets are transported are lower.

It should be noted that although two stepper motors 17,17′ are shown inthis case, a single stepper motor would be sufficient in many cases.With the use of a single motor the belt 15 could be replaced by a wormlead screw or rack and pinion drive arrangement to the moveablecarriage. Two motors allows sufficient power to be obtained to achieverapid displacement of the bracket 14. The use of two motors in parallelis possible because the rubber belt connecting the two motors isflexible.

In yet a further alternative construction the diameters of the pulleys4B,5B,10B,12B will all be of the larger diameter of pulleys 4A,5A,10A,and 12A so as to provide the beneficial effect of corrugating thetransported sheets across their full width.

A second example of a bank note alignment system according to thepresent invention is shown in FIGS. 9 and 10. The apparatus iseffectively the apparatus of FIG. 1 modified such that both ends of thebelts 6 may be moved laterally. This is achieved by having a first setof pulleys 104 non-rotatably mounted to a shaft 102 and a second set ofpulleys 105 non-rotatably mounted to a shaft 103. As with the shafts11,13 the shafts 102, 103 are mounted in bearings (not shown) in each ofthe side plates 7,8. Furthermore, the shafts 102,103 are attached toeach other by respective link plates 118,118′ at each end in such a waythat it allows them to be moved together at approximately right anglesto the side plates. This allows the pulleys 104,105 to be traversed withrespect to the side plates 7,8 whilst maintaining their relative offsetpositions.

Also provided are two stepping motors 117,117′ which are attached to theside plates 7,8 respectfully. Each stepping motor 117,117′ is connectedto a respective drive pulley 116,116′ around which is entrained a belt115. The belt is secured to a bracket 114 which is also secured to theshaft 102. Thus, by suitably operating the stepping motors 117,117′, thebelt 115 is moved to and fro between the side plates 7,8 causingcorresponding movement of the shafts 102,103.

The apparatus of FIGS. 9 and 10 then operates in a similar manner to theapparatus of FIG. 1. Accordingly, when a sheet is fed into the transportsystem, if the sheet is not correctly positioned laterally and/or isskewed, then this is sensed by a detector arrangement (not shown). Themicroprocessor 70 will then compute from this the amount of displacementrequired. This is then achieved by moving either the shafts 11,13 or theshafts 102,103, or all four shafts 102,103,11,13.

Although not shown, it will be realised by a person skilled in the art,that a sensor arrangement, similar to the sensor 51, may be provided forthe belt 115. This will allow the microprocessor 70 to determine therelative position of the pulleys 104,105 with respect to the side plates7,8.

What is claimed is:
 1. A document alignment system comprising a feedsystem, defining an elongate path, for feeding documents along the path,the feed system being adjustable to vary the angular orientation of theelongation path in a lateral plane so as to cause a document to undergoa corresponding lateral shift as the document is moved along the path; adetector for detecting the lateral position of a document upstream ofthe elongate path; and a control system responsive to the detector toadjust the feed system to vary the orientation of the elongate path sothat the document undergoes a desired amount of lateral movement as thedocument is moved along the elongate path.
 2. A document processingapparatus comprising a document alignment system according to claim 1;and a document handling system for receiving aligned documents from thedocument alignment system.
 3. A system according to claim 1, wherein thefeed system comprises at least one endless belt.
 4. A system accordingto claim 3, wherein the control system is arranged to adjust theposition of the endless belt(s) at a location adjacent a downstream endof the elongate path.
 5. A system according to claim 3 wherein thecontrol system is arranged to adjust the position of the endless belt(s)at a location adjacent an upstream end of the elongate path.
 6. A systemaccording to claim 3, wherein the control system is arranged to adjustthe positions of the endless belt(s) at a location adjacent a downstreamend of the elongate path and a location adjacent an upstream end of theelongate path so as to de-skew a document being transported.
 7. A systemaccording to claim 3, wherein the feed system comprises a plurality ofendless belts arranged in upper and lower laterally spaced sets relativeto the elongate path, each belt of the upper set being laterally offsetfrom adjacent belts of the lower set.
 8. A system according to claim 7,wherein the belts of the upper set do not overlap the belts of the lowerset.
 9. A system according to claim 1, wherein the feed system comprisesa pulley mounted on a shaft, the pulley being coupled to the controlsystem for lateral displacement.
 10. A system according to claim 9,wherein the pulley is mounted for lateral movement with the shaft.
 11. Asystem according to claim 10, wherein the pulley is non-rotatablymounted to the shaft.
 12. A system according to claim 1, wherein thefeed system includes an indicator which moves laterally with the feedsystem and is detected by the detector of the control system.
 13. Asystem according to claim 11, wherein the control system adjusts theposition of the feed system until the indicator is located relative tothe detector of the control system such that a document will undergo thedesired amount of lateral movement.
 14. A system according to claim 12,wherein the indicator has a form which varies in the lateral directionso its direction of displacement can be uniquely determined.
 15. Asystem according to claim 14, wherein the indicator is wedge shaped. 16.A method of aligning documents comprising supplying documents to adocument alignment system including a feed system, defining an elongatepath, for feeding documents along the path, the feed system beingangularly adjustable to vary the orientation of the elongate path in alateral plane so as to cause a document to undergo a correspondinglateral shift as the document is moved along the path, a detector fordetecting the lateral position of a document upstream of the elongatepath, and a control system responsive to the detector to adjust the feedsystem so that the document undergoes a desired amount of lateralmovement as the document is moved along the elongate path; detecting thelateral position of each document; and adjusting the feed system to varythe orientation of the elongation path so as to cause the document toundergo a desired amount of lateral movement as the document moves alongthe elongate path.
 17. A method according to claim 16, wherein thedocuments comprise currency that has been used.